Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751105AbdFTGGH (ORCPT ); Tue, 20 Jun 2017 02:06:07 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:46786 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750808AbdFTGGF (ORCPT ); Tue, 20 Jun 2017 02:06:05 -0400 Subject: Re: [RFC v2 00/12] powerpc: Memory Protection Keys To: Balbir Singh , Ram Pai , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <1497671564-20030-1-git-send-email-linuxram@us.ibm.com> <1497935415.2255.1.camel@gmail.com> Cc: dave.hansen@intel.com, paulus@samba.org, aneesh.kumar@linux.vnet.ibm.com From: Anshuman Khandual Date: Tue, 20 Jun 2017 11:35:00 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: <1497935415.2255.1.camel@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable x-cbid: 17062006-0044-0000-0000-0000027068AD X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17062006-0045-0000-0000-000007000C70 Message-Id: <09886a82-872d-8a43-fd61-549cf006ce6e@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-06-20_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1703280000 definitions=main-1706200113 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1257 Lines: 40 On 06/20/2017 10:40 AM, Balbir Singh wrote: > On Fri, 2017-06-16 at 20:52 -0700, Ram Pai wrote: >> Memory protection keys enable applications to protect its >> address space from inadvertent access or corruption from >> itself. > > I presume by itself you mean protection between threads? Between threads due to race conditions or from the same thread because of programming error. > >> >> The overall idea: >> >> A process allocates a key and associates it with >> a address range within its address space. > > OK, so this is per VMA? Yeah but the same key can be given to multiple VMAs. Any change will effect every VMA who got tagged by it. > >> The process than can dynamically set read/write >> permissions on the key without involving the >> kernel. > > This bit is not clear, how can the key be set without > involving the kernel? I presume you mean the key is set With pkey_mprotect() system call, all the effected PTEs get tagged for once. Switching the permission happens just by writing into the register on the fly. > in the PTE's and the access protection values can be > set without involving the kernel? PTE setting happens once, access protection values can be changed on the fly through register.